Peena is Hindi/Urdu for drink, and hence Peekay would mean 'having drunk.'

However, the complete sentence for 'are you drunk?', in the way they have tried to make here, could be 'Peekay aaya hai kya?' or otherwise, 'Piye hue hai kya?' or 'Piye hai kya?' However, 'Peekay hai kya?' wouldn't be heard, at least in the regular Khadi Boli speaking region.

Hence, everybody asking in a promo 'PK hai kya?' wouldn't make sense to me so much as it would have if they had asked something like, 'PK aaya hai kya?' or 'PK aaya kya?' or maybe 'PA hai kya?' which would be like 'Piye hai kya.'

So yes, in a Rajkumar Hirani film, where he likes to keep things quite perfect, this is quite an imperfect sentence for me, especially when the title of the film is involved, and is customized for effect, it's not effective enough. But then, in time the sentence, if too popular, may set its own standards, and settle down in the language, or next to it.